Roller grinding-mill



J. STEVENS. Roller Grinding Mill.

Patented May 25,

N. PETERSrPHOTQUTNOGRAFHER, WAISNYNGYIDN. D. C

UNITED STATES PATENT QFFICE JOHN STEVENS, OF NEENAH, WISCONSIN.

ROLLER GRINDING-MILL.

SPECIFICATION forming part of Letters Patent No. 228,001, dated May 25,1880.

Application filed February 13, 1878.

To all whom it may concern:

Be it known that I, JOHN STEvENs, of Neenah, in the county of Winnebagoand State of Wisconsin, have invented certain new and usefulImprovements in Grinding-Mills and in the Process of Reducing Grain toFlour, of which the following is a specification.

My invention relates to that class of grinding-mills known asroller-mills, wherein two or more rolls or cylinders revolving atdiiferent peripheral rates of speed work against each other; and itconsists in forming the rolls with parallel grooves having roundeddividing-ribs trending lengthwise of the rolls; in laying the ribs insuch direction upon each roll that they cross each other upon thecontiguous surfaces, and in employing, in the process of reducing grainto flour, a series of sets of such rolls graded in respect to fineness01' number of grooves to the inch, with intermediate bolts, the severalsets acting in sue cession of grade.

In the drawings, Figures 1 and 2 are, respectively, an end and a planview of a pair of rolls provided With a dress according to my invention.Fig. 3 is a diagram representing sets of graded rolls and bolts arrangedaccording to my invention.

The object constantly aimed at in the process of reducing wheat to flouris to increase the proportion of middlings and pure flour, and to leavethe bran and germ in a condition most favorable to their eflectual andcomplete separation from the flour-forming particles. Smooth-surfacedrolls flatten the germ and allow the bran to pass in a coarseunpulverized state, and tothis extent accomplish the object; but theyalso cause the middlings to cake or form into flakes or thin disks, thatwill not pass through the meshes of the bolt, and therefore are in theend unsatisfactory. Grooved rolls having sharp edged intermediate ribscut or tear the bran and germ into such fine particles that a largeproportion will pass through ordinary bolting cloth and inevitablyappear in the middlings and flour, from which they can with greatdifficulty be removed.

My invention is designed to overcome these objections and to produce amachine in which the starch and gluten of the berry shall be properlypulverized without caking, while the tenacious portions, constitutingthe husk and germ, shall pass through in a flattened or flaky conditionwithout being much comminuted, thereby greatly increasing the middlingsand improving the quality of flour.

lteferrin g to the drawings, the rolls a 1), constructed preferably ofmetal, are placed side by, side in the same horizontal plane, and gearedto revolve at different peripheral speeds. Each is provided with spiralgrooves running in the same direction and laid near together, thedividing-ribs between these grooves being rounded, as shown moreparticularly in that portion of Fig. 1 inclosed between brackets l 1.These rolls operate in a manner superior to the smooth-surfaced andsharp-ribbed rolls,.

heretofore known, for, unlike smooth rolls, they do not form themiddlings into disks or flakes which require various and intricatesubsequent operations to reduce them to flour, nor do they cut or tearthe bran and germ into fine pieces or particles, as is the case withsharpribbed rolls; but while pulverizing the starch and gluten, theysimply bruise and rub the bran and germ, bringing them to and leavingthem in a form which insures their passage over the tail of the bolt,and therefore their elimination from the middlings and flour.

Since the grooves and ribs are laid in the same direction on both rolls,they will cross each other on the contiguous surfaces and cannotintermesh. The rolls can therefore be run in peripheral contact withoutinjury to the dress or face, and heating of the flour is reduced to aminimum, as contact with the grinding-surface is momentary orinstantaneous.

The dress may vary in number of grooves to the linear inch, as willhereinafter appear, and one set of rolls capable of suitable adjustmentswill be sufficient for general work. I think it beneficial, however, toemployaseries of sets of rolls graded in respect to fineness of dress.The arrangement may be as shown in Fig. 3. The numerals 1 2 3 4,respectively, indicate separate sets of rolls. Each set is composed oftwo rolls geared together so as to revolve with differential motion asto their peripheries, and both rolls of each set have spiral groovesrunning in the same direction, from left to right.

The grooves of rolls A A in the set No. l

are assumed to number about twenty to the linear inch, measuredcircumferentially on the periphery; the grooves of the rolls B B in theset No. 2 to number about twenty-three to the inch of the rolls 0 O, inset No. 3, to number about twenty-eight, and of the finishing-rolls D D,in the fourth set, to range from thirty to thirty-two-that is to say,the range of gradation I have chosen to illustrate my invention is fromtwenty to thirty-two; but the limit admits of more or less variation ineither direction toward or from a dress numbering about seven or eightgrooves to the linear inch.

With wheat and other cereals it will be inadvisable to have more thanfifteen grooves to the inch, at least in the first pair of rolls, andthe number of grooves in any set should never be so great as to causethe ribs to lose their distinctively rounded character or become sopointed as to cut the bran.

The practical operation is as follows: The Wheat to be converted intoflour is fed into a hopper, (not shown in the drawings,) and passesthence between the first set of rolls, A A, the product consisting ofcracked or partly-crushed wheat, and a considerable quantity of flour isdelivered to a bolt, F, and the coarser grades and tailings from thebolting operation are carried to the neXt pair of rolls, B B, which havefiner grooves than rolls A A. The product of rolls B B is, in turn,passed through bolt G, and so the operation goes on by alternatelycracking or grinding and bolting, through the series of machines untilthe desired product has been thoroughly separated from the bran.

I claim as my invention- 1. In a grinding-mill, the combination of rollsgeared to revolve at different peripheral rates of speed and having adress composed of parallel grooves with rounded dividing-ribstrendinglengthwise of the rolls.

2. In a grinding-mill, the combination of rolls geared to revolve atdifferent peripheral rates of speed and having a dress composed ofparallel grooves with rounded dividingribs laid so as to cross eachother on the con- -tiguous surfaces of the rolls.

3. In a grinding-mill, the combination ,of rolls geared to revolve atdifferent peripheral rates of speed and having a dress composed ofparallel spiral grooves with rounded dividingribs running in the samedirection on each roll.

4. The combination of a series of sets of rolls provided with thegrooved dress herein described, and graded in respect to fineness ofdress, with. bolts intermediate between each set and the succeeding setof rolls.

5. The process of reducing grain to flour, consisting in passing itthrough a series of sets of rolls graded in respect to fineness ofdress, and through bolts intermediate between each set and thesucceeding set of rolls.

The above specification of my invention signed by me this 13th day ofFebruary, 1878.

JOHN STEVENS.

Witnesses:

SoLoN O. KEMON, OHAs. A. PETTIT.

